Effects of Unweighting on Heart Rate Response and Speed/Incline Adjustments Necessary in Elite Runners

Document Type

Article

Publication Date

5-30-2012

Publication Title

Medicine & Science in Sports & Exercise Supplemental 2

DOI

10.1249/01.mss.0000417529.22755.ed

ISSN

1530-0315

Abstract

The AlterG Treadmill, which makes use of lower body positive pressure (LBPP), enables runners to train at race-pace speeds yet with variable body weights (BW) and resultant ground reaction forces. The AlterG is marketed as an “unweighting” tool useful during lower body injury. There is lack of research investigating the additional speed and/or incline necessary at lower BW to achieve the equivalent intensity possible at 100% BW.

PURPOSE: To quantify AlterG speed and incline adjustments necessary at two levels of unweighting in order to achieve intensities equivalent to those at 100% BW running.

METHODS: Following an initial V02max test, seven elite male runners (average age = 30.1 yrs; ht = 177.4 cm; wt = 77.1 kg; V02max = 64.1 ml/kg/min) underwent two unweighted running trials (75% BW and 50% BW). The trials ended when subjects reached their heart rate at 90% V02max. Heart rate, speed, and incline were recorded throughout each trial.

RESULTS: When subjects were unweighted to 75% BW and ran at their heart rate equivalent of 70% V02max, they required an average speed increase of 1.7 mph and an average incline increase of 4.3%; at 80% V02max, 2.8 mph and 3.1% incline, respectively; at 90% V02max, 3.4 mph and 2.0% incline, respectively. When subjects were unweighted to 50% BW and ran at their heart rate equivalent of 70% V02max, they required an average speed increase of 2.7 mph and an average incline increase of 5.1%; at 80% V02max, 4.1 mph and 4.7% incline, respectively; at 90% V02max, 3.9 mph and 4.1% incline, respectively. Further, the average speed increase at 75% BW across all target intensities to reach the equivalent heart rate at 100% BW was 3.1 mph, yet there was only a 0.8 mph additional increase necessary when BW dropped from 75% to 50%. Likewise, the average incline increase at 75% BW relative to 100% BW was 3.1%, while the decrease from 75% BW to 50% BW required only an additional 1.9% incline.

CONCLUSION: Unweighting due to LBPP requires an increase in running speed and incline in order to maintain training intensity levels in elite male runners. Since the increases in speed and incline necessary to achieve target intensities do not appear to be linearly related to the level of unweighting, further research is necessary to identify the variables at which maximum intensity can be achieved while ground reaction forces are minimal.

Comments

©2012 The American College of Sports Medicine

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